Adults inhabit inshore waters. Occur in small to large aggregations in weed patches attached to rocks on sand, mostly in Sargassum weeds. Ovoviviparous. The male carries the eggs in a brood pouch which is found under the tail.
H. breviceps is a temperate, southern Australian endemic seahorse, which is most common in the Port Philip Bay region of Victoria (Kuiter 1993). It is also known from Spencer Gulf and St. Vincent Gulf in South Australia, and Forsters Inlet southward to Port Arthur in eastern Tasmania (Lourie et al. 1999). It has also been recorded from Bass Strait (Last et al., 1983). Pogonoski et al. (2002) report that its occurrence in Western Australian waters is, at this stage, unclear. Lourie et al. (2004) note that some specimens from Western Australia have significantly longer, narrower snouts and may represent a separate species. This slender-snout form has only been seen in the northern portion of the species’ range, and is called H. tuberculatus (knobby seahorse) by Kuiter (1993). The range of H. breviceps falls within FAO fisheries area 57.
Extent of occurrence includes Southern Australia, Victoria,Tasmania, and Western Australia. Area of occupancy includes documented populations in Port Philip Bay region of Victoria (Moreau and Vincent 2004), Spencer Gulf and St. Vincent Gulf in South Australia, Forsters Inlet southward to Port Arthur in eastern Tasmania (Lourie et al. 1999) and from the Bass Strait (Last et al. 1983).
Likely to inhabit the Blanche Harbour-Douglas Bank Aquatic Reserve (Marine Protected Area) in Spencer Gulf, Southern Australia (Pogonoski et al. 2002).
Habitat and Ecology
In Port Philip Bay animals occur in small to large aggregations (Kuiter 1993) with male;female sex ratios of 1:1 (Moreau and Vincent 2004). Group (2–5 individuals) occurrence coincides with particular seaweed areas that are the site of early morning social encounters (Moreau and Vincent 2004). Kuiter (2000) suggests that small groups congregate in safe places at night, often high in macroalgae to keep away from crabs on the substrate. Adults exhibit variable site fidelity, with 12 of 38 individuals remaining within a focal study area for five weeks of observation (Moreau and Vincent 2004). Females use significantly larger area than males (Moreau and Vincent 2004).
H. breviceps is thought to breed on an approximately monthly cycle throughout the Austral summer, producing 50–100 young per brood (Kuiter 2000). Males have large pouches that they inflate when courting females. In situobservations indicate that adult seahorses display and interact with potential partners, although not every day, and not necessarily with the same partner at each encounter (Moreau and Vincent 2004). Females transfer batches of eggs (1.6 mm diameter (Vincent 1990) to males during copulation which can take from a matter of minutes to 2.5 days, in ex situ conditions (Kuiter 1993). Kuiter (1993) reports that in captivity, males may accept eggs from more than one female, although this has yet to be observed in natural wild pairs. Larvae have been observed swimming to the surface upon release, where they grasp small bits of weed or debris in surface waters (Kuiter 2000). Kuiter (2000) reports size at settlement to be 25 mm.
Longevity in aquaria is at least 3–5 years (P.Quong, pers. comm. in Pogonoski et al. 2002), but lifespan in the wild is unknown.
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